Variable output pumping means



p 17, 1963 I N. D. GRISWOLD 3,103,890

VARIABLE OUTPUT PUMPING MEANS Filed June 26. 1962 EI El 64 50 l 50 62 582 INVENTOR. A/e/son 0. Gnswo/o United States Patent Ofitice 3,103,890Patented Sept. 17, 1963 3,103,890 VARIABLE OUTPUT PUMPING MEANS NelsonD. Griswold, Lake Jackson, Tex., assignor to The Dow Chemical Company,Midland, Mich., a corporation of Delaware Filed June 26, 1962, Ser. No.205,363 14 Claims. (Cl. 103-38) This invention rel-ates to pumps andparticularly to reciprocating piston pumps which are capable ofdelivering varying volumes of fluid while the piston or pistons of thepump reciprocate at a substantially constant rate.

Other so-called variable volume pumps have been known for many years forspecific uses, but for one reason or another these pumps are not welladapted for use in mobile service, such as oil and gas well or otherearth well treating service, for example. Such service requires maximumutilization of available horsepower to thereby deliver the maximumvolume of pumped fluid against whatever pressure may develop withoutexceeding the strength limits (of the equipment. Such requirementsnecessitate minimum weight "and bulk consistent with the achieving ofother requirements, and ease and reliability in controlling the variablevolume feature of the pump while under load. Exceptional reliability isnecessary because the pump will be used in remote areas where facilitiesare not available for making major repairs and hevcause in well treatingservice equipment breakdown can result in great damage to the well undertreatment. For example, a pump breakdown during a well cementing jobcould result in the cement setting up in the well casing beforedisplacement can be effected between the casing and wellbore wall.

In conventional we-ll treating pumping units a power source or primemover, usually an internal combustion engine, transmission (which mayinclude a torque converter) and the pump are disposed on a truck,trailer, or barge.

Any reduction in weight which can be achieved in the coupling of powerto the pump of the treating unit would, obviously, permit theconstruction of a lighter treating unit or would permit the constructionof a treating unit having an increased pumping capacity (either involume or pressure, or both) within allowable gross weight limitations.

Accordingly, a principal object of this invention is to provide animproved variable volume pumping apparatus which is particularlysuitable for use in treating earth wells.

Another object of this invention is to provide an improved variablevolume pumping apparatus which is compact in size with respect to itspumping capacity and power utilization over a wide range of pumpingpressures.

A further object of this invention is to provide an improved mobilefluid pumping system for well treating service or the like.

In accordance with this invention a piston type positive displacementpump achieves an infinitely variable stroke between maximum and minimumlimits through a controlled variable phase relationship between twomechanically interlocked crankshafts. These crankshafits operate throughconnecting rods to an equal-legged walking beam pinned at its centerlineto a plunger crosshead. Similar planetary gears, with the ring gearsinterconnected by means of a phase control gear, are used to drive thecrankshafts and also to establish and maintain the desired phaserelationship between the crankshafts during operation. By actuating thephase control gear and thus changing the phase of the ring gears whichare coupled to each crankshaft through the planet gears, the

phase relationship between crankshafits and hence the piston stroke maybe changed inversely with the discharge pressure to provide a hydraulichorsepower output desirably matched to the available horsepower of theprime mover.

The invention, as well as additional objects and a vantages thereof,will best be understood when the following detailed description is readin connection with the accompanying drawing, in which FIG. 1 is asimplified plan view, partly broken away and in section, of apparatus inaccordance with this invention;

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is a sectional view taken along the line 33 of FIG. 1; and

FIG. 4 is a fragmentary end view of drive gears 78a, a showing chaindrive coupling between the drive shafts 36, 38.

Referring to the drawing, there is shown variaible volume pumpingapparatus, indicated generally by the numeral 10 mounted on a commonframe (not shown). The apparatus includes a single action reciprocatingpistontype pump 12 (see FIG. 3 especially) whose piston 14 is coupled toa crosshead plunger 15, adapted to reciprocate in the guide 15a, and tothe center of an equallegged walking beam 16 which in turn is coupled atits ends by connecting rods 18, 20 to crankshafts 22, 24, respectively,which are journaled in bearings 17, 17a, 19, 21 and 19a, 21a, forexample.

Each of the crankshafts 22, 24 has a spur gear 23 or 25 coupledcoaxially thereto near the end of the crankshaft which is adjacent to aplanetary gear assembly 30, 32, respectively. The planetary gearassembly 30, shown in section in FIG. 3, is the same as the assembly 32which is shown in plan in FIG. 1.

The sun gear (see FIG. 3, sun gear 34) of each of the planetary gearassemblies 30, 32 is rigidly mechanically coupled to a shaft 36, 38. Theshafts 36, 38 are disposed parallel to each other and are supported bysuitable bearings 40, 42, 44, 45 and 40a, 42a, 44a, respectively. Thesun gears of each of the assemblies 30, 32 are coupled to theirrespective ring gears 26, 28 by pairs of planet gears, the planet gears46, 48 being shown in FIG 3.

The planet gears of each planetary gear assembly 30, 32 are j ournaledon to shafts 50, 52 (and 54, 56 in FIG. 1) which are parallel to the sungear driving shafts 36, 38 and which are fixedly connected by means ofbrackets 59, 61, respectively, to a hollow shaft 58 or 60, each of whichis parallel to and surrounds one of the respective shafts 36, 38 asshown. Each of the hollow shafts 58, 60 is supported in position by twobearings 62 and 64 and 62a and 6401, respectively. A spur wheel 66, 68is disposed on and rigidly coupled to each of the hollow shafts 58, 60,the wheels 66, 68 being equal in size and in the number of teeth theycontain, their gear teeth being coupled to the teeth of the spur wheels23, 25, respectively.

Sprocket wheels 78, 80 are rigidly coupled in a fixed rotationalrelationship to the shafts 36, 38, respectively, near the end of theshaft 36 or 38 which is remote from the planetary gear assemblies 30,32. The sprocket wheels 78, 80 are of equal diameter and have an equalnumber of teeth, and are coupled together by drive chain 79. Means, suchas the spur gear 82, coupled to the end of the shaft 36"and the gear 84coupled to a prime mover 86, couple power to the shaft 36 and thencethrough the sprocket wheels 78, 80 to the shaft 38. The power source 86,which may be an internal combustion engine or a gas turbine, forexample, is diagrammatically indicated by the block 86 and is coupled,as indicated by the shaft 87, to the gear 84.

A rotatable shaft 70, having worms 72, 74 in spaced apart relationshipalong its length, is disposed transversely with respect to the shafts36, 38 and 58, 60. The worms 72, 74 engage teeth 76, 77 on the outerperipheral surface of the ring gears 26, 28, respectively, the pitch ofthe worms in each being equal but in the opposite direction of rotationso that each of the ring gears 26, 28 can be turned the same amount butin opposite direction at the same time. A turning or control means, suchas the spur wheel 88 is rigidly mechanically coupled to the shaft 70whereby the shaft 70 is rotated when the wheel 88 is rotated by means ofa control motor 90 which drives the gear 92 coupled to the gear 88. Eachof the ring gears is coupled coaxially by means of brackets 97, 97a to ashort shaft 94 or 96 which is journaled in bearings 98, 100 and 98a,100a, respectively.

Each of the bearings 17, 17a, 19, 19a, 21, 21a, 62, 62a, 64, 64a, 98,100, 98a 100a, 102, 104, 106, 108, the pump 12, guide a and shaft 70 aremounted on common framework for the apparatus, which framework alsocarries the power source 86, the framework being attached to orsupported by the mobile unit, e.g. a truck, which carries the apparatus.

In operation the apparatus, as shown, (see FIG. 2 particularly) has thering gears 26, 28 arbitrarily so positioned that the crank throws causeone connecting rod (18) to advance towards the piston 14 while the otherconnecting (rod) 29 is moving away from the piston 14. With suchorientation of the crank throws the walking beam rocks but the pumppiston stroke is practically Zero as power from the gear 84 is coupledby means of the gear 82 to the shaft 36 and, by means of the sprocketwheels 78, 80 and chain79, to the shaft 38.

The shafts 36, 38 drive the sun gear (34 in FIG. 3) of each planetarygear assembly 30, 32, respectively. The sun gear of each assembly iscoupled to the ring gear of its assembly 30, 32 through the planet gears(46, 48 in FIG. 3) of the respective assembly 30 or 32. The ring gears26, 28 are held in a fixed position by the teeth of the worm segments72, 74 of shaft 70 engaging the teeth 76, 77 on the outer peripheralsurface of the ring gears except when the shaft 70 is rotated. Thus, theplanet gears of the assembly are rotated on their shafts 50, 52 and 54,56, and, because the ring gears are in fixed position, the rotation ofthe planet gears causes the shafts 58, 60 to be rotated (because thebrackets 59, 61 rotate with the planet gears). Spur wheels 66, 68,rotated bythe shafts 58, 6t) drive the spur gears 23, 25, thus rotatingthe crankshafts 22, 24.

When the stroke length of the piston 14 is to be changed, the shaft 70is turned (as by driving the spur wheel 88 by the gear 90 coupled to themotor 92, for example), the amount of turning depending upon the degreeof phase change desired. As the shaft 70 rotates, the worms 72, 74rotate and, engaging the teeth 76, 77, cause the ring gears 26, 28 torotate. Such rotating of the ring gears is usually at a slow rate ascompared with rate of rotation of the shafts 58, 60. Because the shafts36, 38 (the drive shafts for the sun gears) rotation in the samedirection, the worms 72, 74 and teeth 76, 77 are disposed so that, onrotation of the shaft 70, the ring gears are rotated in opposite radialdirections, e.g. one is rotated clockwise and the other is rotatedcounterclockwise, for example. Thus, even through the crankshafts 22, 24rotate in the same direction, the relative phasing between thecrankshafts 22, 24 is changed as the shafts ring gears 26, 28 arerotated. The crankshafts 22, 24 are considered to be in phase when theirthrows are sooriented that maximum length of piston stroke is achievedas the crankshafts rotate. The crankshafts are considered to be in theirmost out of phase condition when their throws are so-oriented thatminimum stroke length of the piston 14 is achieved. When the length ofthe piston stroke is at a minimum, the movement of the two connectingrods 18, is such that the walking beam pivots around its point ofattachment to the crosshead with little reciprocating motion applied tothe piston 14.

When the phase relationship of the crankshafts is at an intermediatepoint between the in-phase relationship and the maximum out-of-phaserelationship there will be some rocking of the walking beam about itspoint of attachment to the crosshead, and also some forward and backwardmotion of the piston 14.

The apparatus described above provides means whereby constant horsepowermay be applied to the pump 12 even though the pressure head againstwhich the pump works may vary over a wide range. When the pressure headis low enough to permit such operation, keeping the two crankshaftsoperating on an in-phase relationship results in maximum volume beingdisplaced through the pump 12. As the pressure head increases the gear88 is rotated to cause the crankshafts to be moved in an increasinglyout-of-phase relationship with respect to each other so that theavailable driving horsepower may be used to drive the piston .14 inincreasingly shorter strokes and thus deliver less volume at a higherpressure.

Also, since the pump output can be continuously varied betweenpractically no output and maximum output, there is no need for a torqueconverter or an additional speed varying transmission to be interposedbetween the power source and the pump apparatus providing. the couplingbetween the power source 86 and the gear 82 does not cause the shafts36, 38 to be rotated at excessive speeds.

While the apparatus has been illustrated as driving a single barrelsingle action reciprocating piston pump, a triplex pump, either singleor double acting, or other multiple cylinder pump may be coupled tosuitable crankshafts which are substituted for the crankshafts 22, 24and which are driven by the rotating planet gears (46, 48 in FIG. 3).

The apparatus. of the invention permits the power source to operate at asubstantially constant r.p.m. rate even though the pumping rate varieswidely. Thus, this apparatus is well adapted to be driven by turbines orby an internal combustion piston-type engine operating at an optimumr.p.m. rate.

Because the pump is driven by two crankshafts, the bearing loading onthe individual connecting rods is reduced. A single pump may .delivereither a large volume at moderate pressures or smaller volume at highpressures. In fixed stroke reciprocating piston-type pumps a so-calledhigh volume pump has a relatively low maximum pumping pressure in orderto prevent overloading of the connecting rod bearings or to prevent thestalling of the prime mover. Conversely, a so-called high pressure fixedstroke piston pump is limited in the volume it can pump at lowerpressures because of the maximum safe r.p.m. rate of the crankshaft eventhough the connecting rod bearings may not be overloaded and thehorsepower capabilities of the prime mover are not exceeded.

Pumping apparatus in accordance with this invention is more versatilethan conventional apparatus in that it is good both as a highpressure-low volume pumpand as a low pressure-high volume pump and itadmits of continuous variation of the relationship between pressure .orvolume driving operation. Also, because no intermediate torque converteror speed varying transmission is used, the apparatus is more compact andlighter than a conventional unit of smaller work capabilities.

What is claimed is:

l. A mobile pumping unit comprising in combination a prime mover and avariable displacement pump, said pump comprising a cylinder and pistonreciprocal therein, a crosshead, means for mechanically coupling thepiston to the crosshead to reciprocate the piston with reciprocation ofthe crosshead, a walking beam having a central part and two end parts,said walking beam being pivotally coupled at its central part to thecrosshead, a

pair of crankshafts, each of said crankshafts having at least one throw,a pair of connecting rods, one of said connecting rods being pivotallycoupled to one end part of said walking beam and to a throw on one ofsaid pair of crankshafts, the other connecting rod being pivotallycoupled to the other end of the walking beam and to a throw on saidother crankshaft, a pair of planetary gear assemblies each comprising asun gear, at least one planet gear and a ring gear, each of said ringgears having teeth on both the inner and outer peripheral surfaces, one:of said crankshafts being operatively coupled to the planet gear of oneof said planetary gear assemblies, the other of said pair of crankshaftsbeing operatively coupled to the planet gear of the other of theplanetary assemblies, a pair of drive shafts, means for coupling saidprime mover to said drive shafts and for rotating each of said driveshafts at the same rate, one of said drive shafts being operativelycoupled to one of said sun gears, the other of said drive shafts beingoperatively coupled to the other of said sun gears, and at least onephase control gear, said control gear being coupled to the teeth on theouter peripheral surface of said ring gears for varying the radialposition of the ring gear in one planetary assembly with respect to itssun gear and for varying the radial position of the ring gear in theother planetary assembly with respect to its sun gear whereby the throwof one crankshaft has its radial position changed with respect to theradial position of the corresponding throw of the other crankshaft, andmeans for actuating said phase control gear.

2. A pumping unit in accordance with claim 1, wherein said crankshaftsare disposed parallel to one another.

3. A pumping .unit in accordance with claim '1, Wherein said driveshafts are disposed parallel With one another. 4. A pumping unit inaccordance with claim 1, Where in said phase control gear includes meansfor rotating the ring gears in opposite radial direction to one another.

5. A pumping unit in accordance With claim 1, wherein said phase controlgear is disposed along a rod-like member. I

6. A pumping unit in accordance with claim 5, said coupling between eachcrankshaft and its planet gear comprises a hollow shaft surrounding oneof said drive shafts along part of its length, said hollow shaft havingsaid planet gear jcurnaled thereon and being gear couglad to thecrankshaft.

7. A pumping unit in accordance with claim 1, wherein said prime moveris coupled to said drive shaft through fixed-ratio gear means.

8. A pumping unit in accordance With claim 1, wherein said prime moveris a gas turbine.

9. A pumping unit in accordance with claim 1, wherein said prime moveris a reciprocating piston-type internal combustion engine.

10. A pumping unit in accordance with claim 1, Wherein said phasecontrol gear is a Worm gear member having separated worm sections whosepitch is in opposite direction to one another.

11. A pumping unit in accordance with claim 1, Wherein the sun gear,planet gear and ring gear in one planetary gear assembly are the same asthe corresponding part in the other planetary gear assembly.

12. A pumping unit in accordance with claim 1, wherein the longitudinalaxis of the crank throw of each crankshaft is offset from thelongitudinal axis of its crankshaft by an equal amount.

13. A pumping unit in accordance with claim 1, Wherein the point ofcoupling of the crosshead to the walking beam is along a lineperpendicular to and bisecting a line drawn between the points ofcoupling of the connecting rods to the Walking beam.

14. A pumping unit in accordance with claim 1, Where in said means foractuating said phase control gear is a small prime mover.

No references cited.

1. A MOBILE PUMPING UNIT COMPRISING IN COMBINATION A PRIME MOVER AND A VARIABLE DISPLACEMENT PUMP, SAID PUMP COMPRISING A CYLINDER AND PISTON RECIPROCAL THEREIN, A CROSSHEAD, MEANS FOR MECHANICALLY COUPLING THE PISTON TO THE CROSSHEAD TO RECIPROCATE THE PISTON WITH RECIPROCATION OF THE CROSSHEAD, A WALKING BEAM HAVING A CENTRAL PART AND TWO END PARTS, SAID WALKING BEAM BEING PIVOTALLY COUPLED AT ITS CENTRAL PART TO THE CROSSHEAD, A PAIR OF CRANKSHAFTS, EACH OF SAID CRANKSHAFTS HAVING AT LEAST ONE THROW, A PAIR OF CONNECTING RODS, ONE OF SAID CONNECTING RODS BEING PIVOTALLY COUPLED TO ONE END PART OF SAID WALKING BEAM AND TO A THROW ON ONE OF SAID PAIR OF CRANKSHAFTS, THE OTHER CONNECTING ROD BEING PIVOTALLY COUPLED TO THE OTHER END OF THE WALKING BEAM AND TO A THROW ON SAID OTHER CRANKSHAFT, A PAIR OF PLANETARY GEAR ASSEMBLIES EACH COMPRISING A SUN GEAR, AT LEAST ONE PLANET GEAR AND A RING GEAR, EACH OF SAID RING GEARS HAVING TEETH ON BOTH THE INNER AND OUTER PERIPHERAL SURFACES, ONE OF SAID CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE PLANET GEAR OF ONE OF SAID PLANETARY GEAR ASSEMBLIES, THE OTHER OF SAID PAIR OF CRANKSHAFTS BEING OPERATIVELY COUPLED TO THE PLANET GEAR OF THE OTHER OF THE PLANETARY ASSEMBLIES, A PAIR OF DRIVE SHAFTS, MEANS FOR COUPLING SAID PRIME MOVER TO SAID DRIVE SHAFTS AND FOR ROTATING EACH OF SAID DRIVE SHAFTS AT THE SAME RATE, ONE OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO ONE OF SAID SUN GEARS, THE OTHER OF SAID DRIVE SHAFTS BEING OPERATIVELY COUPLED TO THE OTHER OF SAID SUN GEARS, AND AT LEAST ONE PHASE CONTROL GEAR, SAID CONTROL GEAR BEING COUPLED TO THE TEETH ON THE OUTER PERIPHERAL SURFACE OF SAID RING GEARS FOR VARYING THE RADIAL POSITION OF THE RING GEAR IN ONE PLANETARY ASSEMBLY WITH RESPECT TO ITS SUN GEAR AND FOR VARYING THE RADIAL POSITION OF THE RING GEAR IN THE OTHER PLANETARY ASSEMBLY WITH RESPECT TO ITS SUN GEAR WHEREBY THE THROW OF ONE CRANKSHAFT HAS ITS RADIAL POSITION CHANGED WITH RESPECT TO THE RADIAL POSITION OF THE CORRESPONDING THROW OF THE OTHER CRANKSHAFT, AND MEANS FOR ACTUATING SAID PHASE CONTROL GEAR. 